If you have concluded that estrogen based HRT isn't for you though, then yes testosterone can be used by itself.
Some of it will convert into estradiol anyway.
This is often quoted - the conversion of T to oestrogen at inadequate levels of oestrogen, but I have never seen any evidence from trials that this actually happens. If you know of any, then please post!
Yes it is on the steroid metabolic pathway as one of the precursors and is converted to estradiol by the enzyme aromatase, but that's not to say it will actually be converted because of enzyme controls, feedback mechanisms and tissue specific manufacture, so I understand (though my understanding is hazy!)?
The only information I've found on this was the product monograph for the Intrinsa patch discontinued a number of years ago which showed no change in estradiol levels after administration of the T patch after a year, in one of the trials though participants were also receiving estradiol replacement transdermally and orally.
Hurdity x